Something walking upright in Barry County, Missouri

I’m always doing outdoor activities, floating, camping, hiking and recently I’ve had some strange encounters. First, I like to go conservation areas frequently, and at wire road conservation area off of Grisham ford rd. In Crane, I was there with a friend it was just after sunset when something would throw very large rocks into the Crane creek. that’s all it consisted of is splashing into the creek. It sounds like bowling ball sized rocks being thrown into the water making not only a splash but a “ker-plunk” noise. This really made me and my friend wonder what was making this noise. We were very open-minded about what could cause this noise and it happened on multiple occasions, all shortly after sunset when no one else was at the conservation area. We told several people about this and of course everyone would say its probably just ducks, but like I said the objects in the water were very large making a “ker-plunk” noise like a cannon ball. Just as we finally had given up on the search for the cause of the splashing, months had gone by and me and the same friend went on a float trip. It happened to be the forth of July in 2008. We planned to float in my canoe on Flat creek from Jenkins bridge all the way to a low water bridge on flat creek road (a very long float). The float started about mid-day and about half way through the float is was very dark and cloudy so no moon light. It was just pitch dark on the creek and at a slow deep section of the creek we were just quietly floating along not talking when it seemed like we startled something very large about 20ft. Away. It was just standing in the edge of the creek when we startled it, so it stepped out of the creek. You could hear one leg pull out the water followed by one more, and it displaced a lot of water making waves. It made a couple more steps up on land into a very forested area. Me and my friend were stunned, just remaining dead silent and starring at the area were the noise originated. Then, a very large rock was thrown within 5ft. Of the boat, exactly like the occurrences in Crane. Even though we never saw the creature, It was very clear that it was a large bipedal creature because of the very long strides out of the deep water. It seems that we startled it, so it walked just out of sight not really frightened though, then it threw a rock to warn us to get away.